Nucleophilic bodies bonded to siloxane and use thereof for separations from sample matrices

ABSTRACT

A structure comprising bodies having a functional surface property bonded to a substrate via a siloxane polymer adhesive. The structure may comprise a novel composition comprising a siloxane polymer having carbon bodies bonded thereto by direct carbon to silicon bonds. This composition may be used to bond carbon particles through a medium comprising the siloxane polymer to a vitreous, metal, plastic or other nucleophilic substrate. Alternatively, the bodies may comprise alumina, silicon, zeolite, organic polymers or other nucleophilic compositions, which are bonded directly to silicon atoms of the siloxane polymer. To bond carbon or other nucleophilic bodies to the substrate, the substrate is contacted with a mixture of the bodies and a hydrosiloxane polymer. The mixture is heated to cause the polymer to be bonded to the nucleophilic bodies, typically by C--Si, C--O--Si, Si--O--Si or Si--O--Al bonds, and to the substrate by reaction with the surface silanol or other nucleophilic groups. Chromatographic methods using a column comprising the novel composition are also disclosed.

This is a division of application Ser. No. 08/283,210, filed Jul. 29,1994, which is a continuation-in-part of Ser. No. 08/276,048, filed Jul.15, 1994, now abandoned, which is a continuation-in-part of Ser. No.08/201,752, filed Feb. 25, 1994, now abandoned which is acontinuation-in-part of Ser. No. 08/191,644, filed Feb. 4, 1994, nowabandoned.

BACKGROUND OF THE INVENTION

This invention relates to separation of mixtures by differentialadsorption, and more particularly to improved adsorption systems inwhich adsorbent bodies comprising a nucleophilic material, such ascarbon, silica, alumina or a polymer having a hydrocarbon moiety, arebonded to a substrate-via a siloxane polymer. Adsorbent bodiescomprising carbon are preferably bonded to the siloxane polymer via adirect C--Si bond.

Various forms of carbon serve as effective media for chromatographiccolumns and solid phase extraction devices. Conventionally, where carbonhas served as the stationary phase of a chromatographic column, thecarbon is present in the column in the form of packing. However, when asample matrix fluid is passed as the mobile phase through a columncontaining a fine carbon packing, the pressure drop through the columnis generally high. Moreover, there is a tendency for the carbon tobecome entrained in the matrix fluid. Both entrainment and pressure dropcan be minimized by using a granular carbon of relatively large particlesize, but such coarse packing has a low adsorptive surface area per unitof column length and/or low resolution of the introduced analytes.

Adsorbent bodies of other nucleophilic materials, such as alumina,silica, zeolite and porous polymers are preferably also of smallparticle size; and packed columns containing such adsorbent materialstypically present the same pressure drop and entrainment problems aspacked carbon columns.

By binding a relatively fine carbon or other adsorbent material to theinternal wall of a tube, a chromatographic apparatus may be providedwhich presents a substantial adsorptive surface area, yet may beoperated at low pressure drop. By binding a high surface area adsorbentto the interior wall of a column, a column of a given diameter canaccommodate a given flow of sample matrix at a much lower pressure dropthan a column that is packed with an adsorbent of comparable particlesize, and comparable adsorptive surface area per unit of column length.Consequently, at comparable pressure drop, the coated wall column can beof much smaller diameter than the packed column.

It has been found that much enhanced separation is achieved in columnsof very small diameter, especially those in the capillary range, sinceaxial backmixing is greatly minimized. Various adsorbent materials areused in such columns, including porous silica, zeolite molecular sievesand various forms of carbon. Such columns are generally referred to as"porous layer open tubular" (or PLOT) columns. Where a liquid stationaryphase is coated over a porous support, the column may be referred to as"support coated open tubular (or SCOT). If the adsorbent material iscarbon or graphite, capillary columns of this type are conventionallyreferred to "carbon layer open tubular" (CLOT) or "graphite layer opentubular" (GLOT). All operate at low pressure drop by providing anessentially unobstructed path for the mobile phase to flow over theporous adsorbent or support.

Activated charcoal particles have been coated onto the interior wall ofa glass column by using high molecular weight waxes or organic liquidsas binding agents. For example, Vidal-Madjar et al., "Fast Analysis ofGeometrical Isomers of Complex Compounds by Gas-Solid Chromatography,"Gas Chromatograph, Elsevier (Amsterdam 1970), pp. 20-23, describe thepreparation of a capillary column containing graphitized carbon adheredto the interior column wall using a styrene polymer as a form ofadhesive. Another common coating material used for this purpose ispolyethylene glycol, typically modified to contain carboxylfunctionality for greater polarity. Carbon, zeolite, alumina and silicaadsorbent particles have been adhered to the interior wall of a PLOTcolumn using such coatings. However, the coating materials of the abovedescribed type bind to adsorbent bodies via Van der Waals forces only.Consequently, the column must be operated below the temperature at whichthe wax, polystyrene, polyethylene glycol or other bonding agentsoftens, or else the bond between carbon and the glass loses strengthsufficient to resist entrainment. Typically, this means that the columncannot be operated above a limit of about 115° C. Even at temperaturesbelow such limit, the carbon or other adsorbent particles have atendency to break free into the matrix phase as it moves through thecolumn. Moreover, the adsorbent particles are especially prone toentrainment in rinsing liquids or purging gases, which typically move athigher velocities than the sample matrix.

Solid phase extraction devices are advantageously constructed of asingle fiber that may be injected into a sample via the cannula of asyringe; or bundle or cluster of fibers, for example, fibers arrayed inparallel in a manner similar to the bristles of a brush. Particles ofadsorptive material are coated onto the fiber. In other devices known tothe art, the adsorbent particles are enmeshed or otherwise mechanicallytrapped in a woven or blown fiber fabric, typically formed as or cutinto a disk. Immersion of the device in a liquid sample matrix presentsa large area of adsorptive surface on which a solute may be extractedfrom the matrix. A type of solid phase extraction device, commonlyreferred to as a "denuder," is used for selective removal of a componentof a gas sample, such as an air sample. The adsorptive agent of a saidphase extraction device is typically coated onto the surface of glassfibers in a manner comparable to the attachment of adsorptive particlesto the inside wall of a chromatographic column as described above. Thus,activated carbon and other solid phase extraction devices known to theart have suffered from the same disadvantages as their chromatographiccounterparts. Operating temperatures are limited; and the adsorptiveparticles are rather readily wiped off the fiber surfaces by contactwith a sample matrix or rinsing liquid.

The tubular walls of chromatographic columns and the fibers of solidphase extraction devices are both preferably constituted of glass.However, a variety of metals and plastic materials may also be suitable,especially as materials for the walls of a chromatographic column.

A need has existed for an improved means of adhering carbon zeolite,alumina, silica and adsorptive organic polymer particles to the tubularwalls of chromatographic columns and the exterior surfaces of the fibersof solid phase extraction devices. A particular need has existed foradhesives which bond effectively both the materials of an adsorbentbody, such as carbon, zeolite, alumina, silica, and porous organicpolymers, and to the materials of the column wall or fiber surface, suchas glass, metal or plastic. Since glass is ordinarily the preferredmaterial of construction for both column tubes and the fibers ofextraction devices, there has been a particular need for a better formof adhesion of carbon to glass. It has been known that C--OH groups atthe surfaces of carbon particles react with silanizing agents, such asdimethyldichlorosilane, to produce an Si--O--C bond. However, this formof bonding has not heretofore been recognized as effective for attachingadsorbent carbon or adsorptive polymer particles to either the internalwall of a glass chromatographic column or the exterior surface of theglass fibers of a solid phase extraction device. It has also been knownin the art that direct C--Si bonds can be formed at high temperature bysolid phase reaction between carbon and silicon, resulting in theformation of silicon carbide, which is well known for use as an abrasivebut has not had application to the field of chemical separations.

Recently, the literature has reported hydrosilylation reactions ofbuckminsterfullerene, C₆₀, with various silanes. West et al., "C₆₀-Siloxane Polymers from Hydrosilylation Reactions," Polymer Preprints,Vol. 34, No. 1 (1993) describes the reaction of C₆₀ withmethyldimethoxysilane, H(Me₂ SiO)₃ SiMe₂ H, and Me₃ SiO--(--HSiMeO)_(a)--(n-OctSiMeO--)_(3a) --SiMe₃ (DP=30), respectively. The authorsdescribe the resulting products as C₆₀ molecules surrounded andencapsulated by the bound polysiloxane. However, no utility is suggestedfor these compositions.

U.S. Pat. No. 5,308,481 describes a polymeric or siliceous supportparticle suitable for use in chromatographic separations having abuckminsterfullerene covalently bonded thereto. In bonding thebuckminsterfullerene to a siliceous particle, the surface of the silicamay be modified by bonding a silane thereto, heating to polymerize theresulting silicon layer and attaching the buckminsterfullerene to theresultant silicone polymer via a functionality on the fullerene. Forexample, the '481 patent describes reacting a fullerene with adiphenylmethyl silane functionalized silica gel in the presence ofaluminum chloride to produce a structure in which the fullerene is boundto the silica through an O--SiR--C₆ H₄ --linkage.

A general need has existed in the art for securely adhering carbon orother granular or particulate bodies to the surface of a substrate. Byway of particular example, it may be desirable to adhere catalyst bodiesto the wall of reactor vessel, exhaust converter or other tubular fluidflow conduit. Further applications exist in which it may be desirable toadhere fibrous bodies to a substrate surface.

SUMMARY OF THE INVENTION

Among the several objects of the present invention, may be noted theprovision of an improved means of bonding between bodies of granular,particulate or fibrous material and a substrate; the provision of suchmeans for bonding the substrate material of a chromatographic column orsolid phase extraction device and the material of an adsorbent particlesuch as carbon, zeolite, alumina, silica and organic polymers, and inparticular for the bonding of elemental carbon and vitreous substratessuch as silica glasses; the provision of such a bonding means which isstable at temperatures well in excess of 115° C., and preferably inexcess of 300° C; the provision of such bonding means by which carbon orother adsorbent material may be adhered to a glass, metal, or plasticsubstrate; and the provision of such bonding means by which adsorbentmaterial can be bonded to the internal wall of a chromatographic columnor the fibers of a solid phase extractive device.

Further objects of the invention include the provision of an improvedchromatographic column containing a carbon zeolite, alumina, silica orpolymeric adsorbent; the provision of such a column which has a largecarbon B.E.T. surface area per unit length of column or which containsgraphite with effective adsorptive properties; the provision of such acolumn which can be of very small diameter yet be operated at lowpressure drop; the provision of such a column which can be operatedunder varying conditions, including high temperature, withoutentrainment of adsorbent particles in a sample matrix phase; and theprovision of such a column which can be vigorously rinsed without lossof adsorbent particles. Objects of the invention further include theprovision of a solid phase extraction device in which adsorbentparticles are adhered to glass fibers; the provision of such a devicewhich can be used at high temperature without detachment of adsorbentparticles; the provision of such a device which can be vigorously rinsedwithout loss of adsorbent particles; and the provision of means forbonding bodies of a catalytic material to a substrate.

It is a further object of the invention to provide methods for producingthe bonding means, chromatographic columns, solid phase extractiondevices and catalytic systems having the characteristics outlined above.

Briefly, therefore, the present invention is directed to a compositioncomprising a siloxane polymer having bodies of a carbonaceous materialbonded thereto. The carbonaceous bodies comprise elemental carbon or apolymer comprising a hydrocarbon moiety. The bodies are bonded to thesiloxane polymer by direct carbon to silicon bonds between carbon atomsof the bodies and silicon atoms of the siloxane polymer.

The invention is further directed to a structure comprising bodieshaving a functional surface property bonded to a substrate via asiloxane polymer adhesive. The bodies comprise a nucleophiliccomposition bonded directly to silicon atoms of the siloxane polymer.

The invention is further directed to a chromatographic apparatuscomprising a column containing a substrate having adsorbent bodiesbonded thereto through a medium comprising a siloxane polymer. Thebodies comprise a nucleophilic composition bonded directly to siliconatoms of the siloxane polymer.

The invention further contemplates a structure comprising discreteadsorbent bodies bonded to a monolithic substrate through a mediumcomprising a siloxane polymer.

The invention further comprises a chromatographic apparatus comprising acolumn containing a substrate having adsorbent bodies bonded theretothrough a medium comprising a siloxane polymer. The bodies comprisenucleophilic composition selected from among amorphous carbon, graphite,turbostatic carbon, zeolite, alumina, silica, and an organic polymer.

The invention is further directed to a chromatographic apparatuscomprising a column containing a substrate having adsorbent particlesbonded thereto through a medium comprising a siloxane polymer. Theparticles comprise a nucleophilic composition and have an averageparticle size of between about 0.1 and about 10 microns.

The invention is still further directed to a solid phase adsorptiondevice comprising a fiber having adsorbent bodies adhered to a surfacethereof through a medium comprising a siloxane polymer. The bodiescomprise the nucleophilic composition bonded directly to silicon atomsof the siloxane polymer.

The invention is further directed to a chromatographic apparatuscomprising a column containing a substrate having adsorbent bodies of acarbonaceous material bonded thereto through a medium comprising asiloxane polymer. The carbonaceous material is selected from amongcarbon and a polymer comprising a hydrocarbon moiety. The adsorbentbodies are bonded to the siloxane polymer via a C--O--Si linkage.

The invention is also directed to a solid phase adsorption devicecomprising fibers having adsorbent bodies of a carbonaceous materialbonded thereto through a medium comprising a siloxane polymer. Thecarbonaceous material is selected from the group consisting of carbonand a polymer comprising hydrocarbon moiety. The adsorbent bodies arebonded to the siloxane polymer via a C--O--Si linkage.

Further contemplated by the invention is a method for bonding bodieshaving a functional surface property to a substrate through a mediumcomprising a siloxane polymer. The bodies comprise a nucleophiliccomposition. In the method, the substrate is contacted with a mixture ofthe bodies and a hydrosiloxane or halosiloxane polymer. The mixture isheated to cause the polymer to be bonded to the bodies and to thesubstrate.

The invention is further directed to a solid phase adsorption devicecomprising a substrate having adsorbent bodies bonded thereto through amedium comprising a siloxane polymer. The bodies comprise a nucleophiliccomposition selected from among amorphous carbon, graphite, turbostaticcarbon, zeolite, alumina, silica, and an organic polymer.

The invention is further directed to a solid phase adsorption devicecomprising a substrate having adsorbent particles bonded thereto througha medium comprising a siloxane polymer. The particles comprise anucleophilic composition and have an average particle size of betweenabout 0.1 and about 10.

The invention is further directed to a chromatographic method forseparation of the mixture of compounds. The mixture is introduced into achromatographic column containing a substrate having adsorbent bodiesbonded thereto through a medium comprising a siloxane polymer. Theadsorbent bodies comprise a nucleophilic composition bonded directly tosilicon atoms of the siloxane polymer. Components of the mixture areeluted from the column.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photomicrograph of a transverse cross section of a tubularglass column wall having multiple layers of carbon particles embedded ina siloxane polymer webbing attached to the interior surface of the wall;

FIG. 2 is a schematic drawing corresponding to the photomicrograph ofFIG. 1;

FIG. 3 illustrates a solid phase extraction device comprising a syringecontaining a fiber having a coating of adsorbent particles embedded in asiloxane polymer webbing;

FIG. 4 is a transverse cross section of one of the fibers of FIG. 3illustrating multiple layers of adsorbent particles embedded in asiloxane polymer webbing attached to the exterior surface of the fiber;

FIGS. 5 to 8 are chromatograms obtained by gas chromatography of variousmixtures using a PLOT column of the type illustrated in FIGS. 1 and 2;

FIGS. 9 and 10 are schematic illustrations of "denuder" type solid phaseadsorption devices utilized for removing select components of an airstream or other gas sample; and

FIGS. 11 to 19 are further chromatograms obtained by gas chromatographyof a variety of mixtures using PLOT columns of the type illustrated inFIGS. 1 and 2.

Corresponding reference characters indicate corresponding parts in theseveral views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the invention, bodies of granular particulate orfibrous material are bonded to a substrate via a medium comprising asiloxane polymer adhesive. As used herein, the term "functional surfaceproperty" means that the surface is capable of some physical or chemicalfunction such as, for example, adsorption or catalysis, or provides anextended surface for support of another material which has a usefulchemical or physical property. Advantageously, the bodies comprise thestationary phase of a chromatographic apparatus, or of a solid phaseextraction device. As used herein, the term "bodies" is generic tocarbon, zeolite, alumina, silica, organic polymers or other materials invarious physical or geometric forms, including particles, fibers,granules, and masses of essentially any size or shape. In thedescription, the term "particles" is primarily used, since this is theform most often preferred in applications of the invention tochromatographic columns and solid phase extraction devices. The bodiescomprise a nucleophilic material that is reactive with silyl hydridegroups of a hydrosiloxane polymer adhesive or the silyl halide groups ofa halosiloxane polymer adhesive medium. The substrate has a surfacecomposition that is preferably also nucleophilic and reactive with ahydrosiloxane or halosiloxane polymer to form a strong chemical bond.

Bonding of the nucleophilic composition of the particles, granules orother bodies to the siloxane polymer comprises a covalent bond whichconsists either of direct bonds between atoms of the particle andsilicon atoms of the siloxane polymer or linkages that consist of anoxygen atom bonded to both an atom of the particle and a silicon atom ofthe siloxane polymer. It will be understood that, depending on thestructure of the siloxane polymer and the exact character of theparticle surface, both types of such bonds may be involved. Where thesurface of the particle comprises functional groups such as halo, amino,isocyanate, isothiocyanate, sulfhydryl, etc. bonding of the particle tothe siloxane polymer may comprise additional linkages resulting fromreaction of such functional groups with moieties of the siloxanepolymer.

According to a particularly preferred embodiment of the invention, aunique process has been discovered for the preparation of a novelcomposition of matter which has valuable and important properties in awide variety of applications. A novel composition of matter comprises asiloxane polymer having adsorptive carbon or organic polymer bodiesbonded to it by direct carbon to silicon bonds. Further in accordancewith the invention, it has been found that the novel direct C--Si bondbetween an adsorptive carbon or polymer body and a siloxane polymerprovides a highly advantageous means for bonding of such adsorbentparticles to glass. This novel structure has further been found toprovide a novel and valuable means for bonding of adsorbent carbon orpolymer particles to the wall of a glass chromatographic column or theglass fibers of a solid phase extraction device.

More particularly, the preferred composition of matter of the inventioncomprises a structure in which the C--Si bond is contained in a moietycomprising: ##STR1## in which the carbon to carbon to silicon bond is atthe surface of the carbon or polymer particle. In most instances, thehydrosilyl group may be expected to add across a double bond at thecarbon surface, or across a terminal double bond or aromatic double bondof an organic polymer, to form the structure of Formula I.

A very wide variety of substituents can be attached to the free bonds ofthe structure of formula I. Preferably, however, the moiety of formula Ihas the structure: ##STR2## wherein R is hydrogen, substituted orunsubstituted hydrocarbyl, alkoxy, aryloxy, nitro, cyano, amino or an--O--Si.tbd. moiety. Preferably, the R group is hydrocarbyl, and morepreferably a C₁ to C₂₅ alkyl group, most preferably a lower alkyl groupsuch as methyl, ethyl, propyl, isopropyl, n-butyl, amyl, hexyl, decyl orthe like. R may also encompass halo-, alkoxy-, aryloxy-, amino- andcyano- substituted alkyl groups, such as for example, --(CH₂)_(x) CN,where x is 1 to 8, --CH₂ CH₂ CF₃, --(CH₂)_(x) CF₂)_(y) CF₃, where x is 2to 5 and y is 0 to 2, --(CH₂)_(z) (CF₂)_(y) CF(CF₃)[OCF₂ CF(CF₃)]_(x) F,where z is 2 to 5, y is 0 to 2 and x is 1 to 5, and --CH₂ CH₂ CH₂ (OCH₂CH₂) x_(x) OR' where x is 0 to 5 and R' is alkyl or aryl. As a furtheroption, R can comprise the structure ##STR3## where R⁹, R¹⁰, R¹¹, R¹²,R¹³, R¹⁴, and R¹⁵ are hydrogen or hydrocarbyl, Ar is aryl and p/(p+q) isbetween about 0.01 and about 1.0. Primary or secondary substitutedhydrocarbyl groups having a carbon chain length of greater than about 5are preferably not used, in order to avoid undesired cross-linkingreactions between siloxane polymer chains. Alternatively, R may be anaryl group, for example, a group having the structure: ##STR4## whereR¹⁶ may be alkyl, aryl, alkoxy or aryloxy having 1 to 25 carbon atoms,amino, nitro, halo or cyano. Suitable aryl groups include phenyl, orsubstituted phenyl such as nitrophenyl, chlorophenyl, toluyl or anilino.R and/or any of R¹ to R¹⁶ may also comprise a heterocyclic group such asfuryl, thienyl, pyridinyl, etc. The ##STR5## group is preferably arepeating unit of an organo siloxane polymer residue which morepreferably has the formula: ##STR6## where R is as defined above and R¹,R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are independently selected from amongsubstituted and unsubstituted hydrocarbyl, nitro, cyano, and an--O--Si.tbd. moiety, m+n is such that the average molecular weight ofthe polymer is between about 80,000 and about 2 million, preferablybetween about 250,000 and about 500,000, and m/(m+n) is between about0.01 and about 1.0, more preferably between about 0.01 and about 0.2.The molecular weight distribution is preferably narrow, i.e., ±5000Daltons, as provided, for example, by chromatographic purification of acrude organosiloxane polymer. Thus, number average and weight averagemolecular weight are essentially the same. Where any of R¹, R², R³, R⁴,R⁵, R⁵, R⁶, R⁷, and/or R⁸ is hydrocarbyl, it may be any of the groupsthat may constitute R in Formula II. Where any of R, R¹, R², R³, R⁴, R⁵,R⁶, R⁷, and/or R⁸ is --O--Si.tbd., it advantageously constitutes theresidue of a surface silanol residue of a vitreous substrate, thusserving as a bridge between the substrate and the siloxane polymer. Inthis way, the adsorptive carbon or organic polymer particle may be boundto a glass or other vitreous substrate via the siloxane polymer, thepolymer being bound to the carbon via the novel C--Si bond, and to theglass via one or more --Si--O--Si--bonds.

It has been found that the direct carbon to silicon (--C--Si.tbd.) bondin the structure of Formula IV has a very high thermal stability. Moreparticularly, it may be exposed to temperatures substantially in excessof 300° C. without breaking down.

Preferred organic polymer adsorbents useful in the compositions andconstructions of the present invention include poly(divinylbenzene),copolymers of styrene and divinylbenzene, such as that comprised by theporous nonionic polymeric adsorbent material sold under the tradedesignation XAD™ by Supelco, Inc. of Bellefonte, Pa., polystyrene, theporous highly crosslinked methacrylate copolymer resins comprised by theadsorbent material sold under the trade designation Amberchrom™, also bySupelco, acrylic ester copolymers, acrylonitrile-divinylbenzenecopolymers and various polymers comprising an aromatic backbone oraromatic pendent groups. A variety of other crosslinked polymericmaterials may be used, provided that they comprise a hydrocarbon moietyto which the polysiloxane may attach, preferably by a direct C--Si bond.Thus, the polymeric material of the organic polymer adsorbents is notlimited to exclusively hydrocarbon polymers as long as a hydrocarbonmoiety is available for reaction with the polysiloxane. Preferably, thehydrocarbon moiety includes a C═C double bond that is reactive with ahydrosilyl moiety of a hydrosiloxane polymer to produce a.tbd.C--Si.tbd. linkage of the type described hereinabove in the case ofadsorbent carbon bodies. Alternatively, methylene, or pendent orterminal methyl groups of the polymer constituting the adsorbentmaterial may react with a halosiloxane moiety of the siloxane polymer.As indicated, the organic polymer resins used as the material ofadsorbent bodies are preferably substantially crosslinked. The degree ofcross-linking should be sufficient to provide the desired swellabilitycharacteristics, as is well known to those skilled in the art.

Further in accordance with the invention, it has been found that bodiescomprising other nucleophilic materials, such as adsorbent bodies ofzeolite, alumina, and silica, may be effectively and securely bound to aglass substrate via a siloxane polymer medium. It has also been foundthat bodies comprising carbon, zeolite, alumina, silica, organicpolymers, and other nucleophilic materials may be bound via a siloxanepolymer medium to a substrate having a nucleophilic surface compositioncomprising metal or plastic.

A zeolite molecular sieve is typically bound to a silyl hydridepolymeric adhesive via an Al--O--Si or Si--O--Si linkage. Alumina isbound through an Al--O--Si linkage; and activated silica or silica gelis bound through an Si--O--Si linkage. Each of these provides strongadherence of the adsorbent material to the siloxane adhesive. Becausethe siloxane also adheres strongly to the substrate material, the novelstructures of the invention may be embodied in a chromatographic columnor solid phase extraction device which can be contacted with a flowingmatrix phase, purge gas, or rinsing solvent without dislodging thebodies of adsorbent or other material from the substrate.

A metal substrate may be bound to the siloxane polymer through a varietyof linkages, depending on the nature of the metal, the natural surfacefilm it may form, or the preliminary surface treatment to which it issubjected. Among the preferred metals for use as chromatographic columnsubstrates are stainless steel, nickel, molybdenumand titanium. However,hydrosiloxanes and halosiloxanes readily react with essentially anynucleophile. Thus, a wide variety of metals can be used, since thesurfaces of metals commonly comprise compositions of nucleophiliccharacter. Some metals may react with silyl hydride or silyl halidemoieties to form direct metal to silicon bonds. Others may react withoxides or hydroxides at the surface to bond to the siloxane through anoxygen linkage.

Plastic or resinous materials that may constitute a column wall, or thefibrous substrate of a solid phase extraction device include, forexample, polyethylene, polypropylene, and poly(tetrafluoroethylene). Asin the case of organic polymeric adsorbents, the polymeric material ofthe plastic substrate preferably comprises a hydrocarbon moiety withwhich a hydrosilyl or halosilyl moiety can react. Attachment of thesiloxane polymer to the plastic substrate is preferably through a directC--Si bond, as in the case of the bond between the siloxane polymer andthe organic polymer of a polymeric adsorbent.

In accordance with the preferred method of the invention for bondingelemental carbon to a vitreous or other substrate, the composition ofFormulae I, II, and IV is prepared by reaction of a particulate carbonwith an organosiloxane polymer containing silyl hydride groups andcorresponding to the formula: ##STR7## where R, R¹ through R⁸, m+n andm/(m+n) are generally as defined above, but at least one of R¹ throughR⁸ is hydrogen (or --O--Si.tbd.). Where any of R¹ through R⁸ is--O--Si.tbd., it may comprise a moiety of a branched organopolysiloxane,e.g., a polymer wherein R of Formula V has the structure of Formula IX,or a polymer comprising the structure: ##STR8## where R, R¹ through R⁸and R¹⁷ through R²² have the same definition as R¹ through R⁸ in FormulaV, m' and n' have the same definition as m and n in Formula V, and m'/(m'+n') falls within the same range as m/(m+n). Otherwise, at the startof the process of preparation, none of R or R¹ through R⁸ is ordinarily--O--Si.tbd..

However, where the purpose is to bond carbon particles to a vitreous orother substrate, the reaction is preferably carried out in the presenceof that substrate, so that hydrosilyl groups of the siloxane polymerreact to bind the polymer both to the carbon particle and to thevitreous substrate. In this instance, whether the siloxane with whichthe carbon reacts initially contains --O--Si.tbd. substituents willdepend on the relative rates of reaction of the polymer with the carbonand the substrate, respectively (and on whether the bond to thesubstrate comprises an .tbd.Si--O-- linkage, as it typically does wherethe substrate is vitreous). Although we do not wish to be held to aparticular theory, it is believed that hydrosilyl groups of the polymerreact with residual α-olefinic hydrogens of the carbon particle. Wherethe substrate is vitreous, hydrosilyl groups are also believed to reactwith residual silanol groups of the substrate. Thus, the reaction isbelieved to proceed according to the following scheme: ##STR9##Accordingly, it is generally preferred that at least one of R¹ throughR⁸ be hydrogen, so that the polysiloxane has a hydrosilyl functionalityof at least 2. Having such structure, the polymer can react with bothcarbon at the surface of the carbon particle, to provide the thermallystable .tbd.C--Si.tbd. bond, and silanol groups at the surface of theglass to provide the --Si--O--Si bond through which the polysiloxane isbound to the glass. While a hydrosilyl functionality of 2 is the minimumrequired for the above reaction, it is generally preferred that betweenabout 1% and about 5% of the R¹ through R⁸ substituents on the backbonesilicon atoms be hydrogen. In part, the hydrosilyl functionality may beprovided by dihydrosilyl groups but, in any case, it is especiallypreferred that m/(m+n) in Formula VI be between about 0.04 and about0.10. Where the carbon is a carbon molecular sieve, the proportion ofhydrogen substituents is optimally about 5% and m/(m+n) about 0.5. Wherethe carbon is graphite, the proportion of hydrogen substituent isoptimally about 10% and m/(m+n) about 0.10.

Surface chemistry of the carbon particle may be complex, but the processof the invention is effective to produce direct carbon to silicon bondsbetween carbon of the particle and silicon of the siloxane polymer. Insome instances, surface carbons of the carbon particle may be entirelybonded to other carbons, e.g., by carbon to carbon double bonds, inwhich case a hydrosilyl group may be expected to add across the doublebond to produce the structure of Formula I. Alternatively, there may becarbon free radicals at the surface, which react directly with thehydrosilyl group to form the Si--C bond, the hydrogen either reactingwith other free radicals, adding across carbon to carbon double bonds,or being released in the form of molecular hydrogen or bound to otherelements. In some instances, elements such as hydrogen, oxygen ornitrogen are initially bound to some of the carbons with which thehydrosilyl group reacts. However, the molar proportion of such boundsurface elements is much lower than the proportion of hydrogen in even ahighly unsaturated hydrocarbon. As discussed hereinbelow, oxygen ispreferably removed prior to reaction with the siloxane poller, butquantitative removal of oxygen may not be entirely achieved. Wherehydrogen, oxygen, or nitrogen are bound to the surface, thehydrosilylation reaction may cause by-product H₂, H₂ O, or NH₃ to bereleased in the reaction. At the reaction temperature, these by-productgases are readily vented from the reaction system.

In accordance with the invention, essentially any of the various formsof carbon can be bonded to a siloxane polymer via direct C--Si bonds.These include for example, graphite, graphitized carbon black,turbostatic carbon, glassy carbons, and carbon in any of its otheramorphous conformations, prominently including carbon molecular sievesor activated carbon molecular sieves of the type suitable for use inchromatography. Prior to reaction with the siloxane polymer, the surfaceof the carbon particle is prepared for the reaction by treatment toremove bound surface oxygen. Surface oxygen is removed by heating thecarbon in an inert or reducing atmosphere at a temperature preferably inexcess of about 225° C., more preferably above 300° C. Optionally, thecarbon surface may be treated in other ways to enhance the formation of.tbd.C--Si.tbd. bonds by reaction of carbon at the particle surface with.tbd.Si--H groups of the siloxane polymer. For example, free radicalsites may be formed on the carbon surface by treatment either withhydrogen or with a plasma, e.g., a plasma of propylene or otherhydrocarbon monomer. By chemical vapor deposition, pyrolyric carbonsources such as unsaturated hydrocarbons may be deposited on the carbonsurface, thereby providing --C═C-- groups at the surface which can bereacted with hydrosilyl groups of the polymer.

After the carbon surface has been prepared by removal of bound oxygen,the substrate surface is contacted with a mixture of the elementalcarbon and the hydrosiloxane polymer, and the mixture is heated to causethe polymer to be bonded to the carbon particles by direct carbon tosilicon bonds, bonded to a vitreous substrate by reaction with surfacesilanol groups, or bonded to other substrates via the linkages discussedabove. Preferably, the polysiloxane polymer is dissolved in an organicsolvent, the carbon particles are slurried in the resulting solution,and the slurry is heated at a temperature in excess of 200° C.,preferably in excess of about 250° C., to effect the --C═C--/.tbd.Si--Hreaction. The reaction can be carried out at lower temperature, forexample, in the range of between about -25° and about 150° C. in thepresence of a catalyst such as salts of aliphatic carbon acids.Reactions of olefins with polymethylhydrosiloxanes have beenaccomplished with tin hydride, platinum or rhodium catalyst; andreduction of aldehydes and ketones has been done with tributyltin,(dibutylacetoxytin)oxide, Pt/C or Pd/C). Where the reaction is carriedout for attachment of carbon particles to the inside wall of achromatographic column, the use of a catalyst is preferably avoidedsince the presence of residual catalyst in the resultant carbon coatingmay interfere with chromatographic separations. In other applications,such as solid phase extraction devices, the presence of residualcatalyst may cause no particular difficulty. However, generally, it ispreferred that the reaction be promoted by conducting it at elevatedtemperatures, above 200° C., rather than by the presence of a catalyst.

Adsorbent bodies of zeolite, organic polymer, activated alumina,activated silica, silica gel, or other nucleophilic material may bebonded to a vitreous or other substrate using substantially the samemethod that is used to bond carbon particles to a substrate. Ahydrosiloxane polymer bonds with a zeolite molecular sieve according thereaction: ##STR10## Bonding of alumina to a hydrosiloxane proceeds inthe following manner: ##STR11##

The reaction of activated silica or silica gel with a hydrosiloxanepolymer proceeds as follows:

    .tbd.Si--OH+.tbd.Si--H→.tbd.Si--O--Si.tbd.+H.sub.2

The conditions of the reaction are substantially as described above inthe case of carbon particles.

To bond adsorbent particles to a substrate, the particles are preferablysuspended in a solution of the polysiloxane, and the substrate iscontacted with the suspension at a temperature in the aforesaid range.Essentially any organic solvent that provides effective solubilizationof the organosiloxane polymers and wets the carbon particles can be usedfor the reaction. Among the organic solvents that may conveniently beused are alcohols such as methanol, ethanol, isopropanol and n-butanol,ketones, such as methyl ethyl ketone, methyl isobutyl ketone, and methylisopropyl ketone, ethers such as diethyl ether, methyl ethyl ether anddipropyl ether, esters such as ethyl acetate, methyl butyrate, or amylacetate, aromatic solvents such as benzene, toluene and xylene,halogenated solvents such as chloroform, trichloroethane, anddichloromethane, and other common solvents such as dimethylformamide,dimethyl sulfoxide, tetrahydrofuran, etc. Aprotic solvents such ascarbon disulfide and acetonitrile are also useful. Preferably, thesolvent used is effective to wet the carbon particles so that they arereadily suspended in the polysiloxane solution. Thus, for example, wherethe particulate material to be bound is an amorphous carbon produced ata temperature below about 1000° C., it is typically acidic; and in thiscase a halogenated solvent such as dichloromethane may be preferred. Forgraphitic carbon, which is produced at temperatures in excess of 2500°C., tetrahydrofuran is especially preferred.

It is important to maintain the reaction mixture as substantially freeof moisture. Since the solvent is the most common source of moisture, itis therefore preferred that the moisture content of the solvent be notgreater than about 50 ppm, preferably not greater than about 10 ppm.Conveniently, the siloxane polymer is dissolved in the solvent with aidof agitation or exposure to ultrasound. Mechanical agitation orsonication are also preferably used to aid in obtaining a uniformdispersion of the carbon particles in the solution.

Concentrations and ratios of reactants are not narrowly critical; nor ispressure. Conveniently, the siloxane content of the solution may bebetween about 5 and about 100 gpl, and the concentration of carbon orother dispersed solid bodies in the pre-reaction slurry may be in therange of between about 1 and about 500 gpl, ordinarily 10 to 100 gpl.More concentrated coating solutions, in the range of 35 to 80 gpl can beused to provide multiple layers of carbon in a single coat.Concentrations in the 10 to 30 gpl range are generally effective toprovide only a single layer of carbon particles of typical size, e.g.,0.2 to 1 micron. Nonetheless, coatings having multiple layers of carbonparticles can be obtained from such relative dilute compositions byapplying the coating in multiple cycles.

The reactions are readily conducted at ambient pressure, but pressuresranging from a high vacuum, -29.90" Hg, to a positive pressure of up to10,000 psi can be tolerated without adverse effect on the reaction. Whenthe slurry of carbon particles in siloxane solution has been broughtinto contact with the substrate, the solvent is removed and the siloxanereacted with the carbon particles and the substrate. The solvent may beremoved in the course of heating the solution to reaction temperature.Use of vacuum or an inert purge gas may assist in solvent removal. Afterthe solvent has been removed, the carbon/siloxane polymer mixture andthe substrate surface with which the mixture is in contact are heated toa temperature in excess of about 200° C. to effect reaction betweenhydrosilyl groups of the polymer and surface carbon of the particle, andbetween hydrosilyl groups of the polymer and nucleophilic surface groupsof the vitreous substrate. In the case of a vitreous substrate, thehydrosilyl groups of the siloxane polymer are reactive with silanolgroups of the substrate. Where the substrate is metallic, the hydrosilylgroup may react with surface oxide, hydroxide or elemental metal.Plastic substrates react in a manner similar to the organic polymers ofan adsorbent body. The weight ratio of carbon to polysiloxane may varyfrom 1:100 to 100:1, but is conveniently between about 1:1 and about4:1, most preferably between about 1.5:1 and about 3:1. The weight ratioof carbon to substrate is governed by the carbon loading that isrequired for the chromatographic or other application involved. Thisloading may vary widely, as discussed hereinbelow.

Either static or dynamic coating methods may used in applying a coatingcomprising single or multiple layers of carbon particles. In the staticmethod, a slurry of carbon particles in a siloxane polymer solution isapplied as a wet coating to the surface of the substrate, and thesolvent removed by application of heat and/or vacuum. Depending on theconcentration of carbon particles and the viscosity of the solution, acoating of up to six carbon particles in thickness may be obtained in asingle coating cycle. According to the dynamic method, the slurry isforced from a reservoir through a tubular column under inert gaspressure. A slug of the slurry moves ahead of the gas phase, leavingbehind a film adhering to the interior column wall. As the slug movesforward, an annular transition segment of the slurry, having a roughlyconical inside surface, moves along the wall behind the slugintermediate the slug and the wet, stable cylindrical film that isdeposited on the wall. The thickness of the stable film is a function ofthe angle between the wall and the interior conical surface of thistransition segment. It has been found that thicker films are associatedwith both high carbon concentration in the slurry and a relatively steepangle between the slug and the substrate, i.e., both the advancing angleat which the front face of the slug meets the substrate, and thetrailing angle between the transition segment and the substrate; andfurther that the steepness of these angles varies directly with the gaspressure. For example, a coating having a thickness of as many as threecarbon particles of 0.5 micron diameter may be produced in a single passon the inside wall of a glass column having an I.D. of 0.53 mm, byapplication of a slurry having a carbon concentration of between about30 and about 50 gpl under nitrogen or helium pressure of 20 psi or more.By way of further example, if a slurry having such concentration, and avolume approximately one third that of the interior portion of thecolumn, is provided in a reservoir, and the entire contents of thereservoir forced through the column at a pressure of 15 psig,approximately one half of the volume of the slurry originally providedin the reservoir remains as a wet coating on the interior column wall.As in the case of the static coating method, solvent is removed byapplication of heat and/or vacuum. In the dynamic method, the inert gasmay conveniently serve as a carrier gas for assisting removal ofsolvent. In both the static and dynamic method, the reaction between thesiloxane and both the carbon and the substrate is effected bypost-heating to a temperature in the range noted above.

The bonding medium of the invention provides a highly stable bondbetween the inside wall of a glass, metal or plastic chromatographiccolumn and a stationary phase adsorptive medium comprising carbon ofvery fine particle size, e.g., between about 0.1 and about 100 μM havinga surface area of between about 1 and about 3000 m² /g. Moreparticularly, columns can be constructed using graphitic carbon having aB.E.T. surface area in the range of about 2 to about 100 m² /g, or fromcarbon molecular sieves having B.E.T. surface areas in the range ofbetween about 500 and about 1300 m² /g. Particularly preferred carbonmolecular sieves have a particle size of between about 0.2 and about 2μM , a total pore volume of between about 0.1 and about 3 cc/g, amacropore (diamater>500 Å) volume of between about 0.1 and about 2.0cc/g, a mesopore (diameter between 20 and 50 Å) of between about 0.1 andabout 2.0 cc/g, and a micropore (diameter 3 to 20 Å) of between about0.1 and about 2.0 cc/g. Graphitic carbons are generally non-porous andpresent an external surface area in the range of 1 to 100 m² /g.However, a useful graphitized carbon sold by Supelco under the tradedesignation Carbopack Y has a B.E.T. surface area of about 250 m² /g andcomprises a modest level of microporosity, less than about 0.5 cc/g.PLOT columns having an adsorptive surface comprising such carbonadsorbents may be of very small diameter, in the capillary range, yetpresent a very high adsorptive surface area per unit of column length,and be subject to operation at very low pressure drop. Thus, for aservice in which a packed column would need to be operated at a pressureof 40,000 psi, the coated wall capillary type chromatographic column ofthe invention can be operated at a pressure of only 4 psi.

Absorbent bodies comprised of zeolite, alumina, organic polymers, orother nucleophilic may be adhered to a vitreous, metal, plastic or othernucleophilic substrate by the medium of a hydrosiloxane polymer. Themethod is essentially as described above, except that zeolite, silica,and aluminum are not deoxidized prior to the bonding reaction. Nor is itnecessary or appropriate to attempt to deoxidize an organic polymer. Inany event, the adsorbent bodies are slurried in a hydrosiloxane polymerof the same character as that described above, and in the same range ofconcentrations and the slurry is applied to the substrate and reactedunder substantially the same conditions as those described above. Wherethe adsorbent material or the substrate is comprised of an organicpolymer, the temperature should be controlled in a range which will notadversely affect the dimensional stability and/or mechanical propertiesof the polymer or, in the case of a porous polymer adsorbent material,adversely affect the porosity or B.E.T. surface area of the adsorbentbodies. The temperature limits of such materials are well known to theart and easily accessible through standard literature. Thus, thoseskilled in the art will be aware of the temperature limitations that mayapply to any particular polymeric material. Where the temperature mustbe controlled at a relatively low level, the reaction is carried outsatisfactorily by allowing additional reaction time. For example, apolyethylene or polypropylene substrate may be bonded to a polysiloxanepolymer at a temperature in the range of between about 100° C. and about150° C.

Adsorbent bodies of zeolite molecular sieves typically have a particlesize of between about 0.1 and about 5 microns, an average pore volume inthe range of between about 0.3 and about 0.7 cc/g, and an average poresize in the range of about 5 Angstroms. The B.E.T. surface area ofzeolite molecular sieves is generally in the range of about 300 to about400 m² /g.

Adsorbent bodies of activated alumina are generally in the submicronparticle size range, i.e., between about 0.1 and about 5μ. Activatedalumina has an average pore size in the range of about 0-100,000Angstroms, a pore volume of between about 0.25 and about 1 cc/g, and aB.E.T. surface area in the range of about 300 to about 400 m² /g.

Activated silica adsorbent bodies have a particle size of between about1 and about 10, an average pore size of between about 0 and about 1000A, and a pore volume of between about 0.5 and about 20 cc/g. Silica gelhas an average pore size in the range of between about 3 and about 500A°, and an average pore volume in the range of between about 0.5 andabout 20 cc/g, and is available in a typical particle size of betweenabout 1 and about 1,000. B.E.T. surface area is in the range of betweenabout 20 and about 400 m² /g in the case of activated silica, andbetween about 50 and about 1300 m² /g in the case of silica gel.

Porous organic polymers produced by emulsion polymerization may bemonodisperse (with respect to particle size), i.e., narrowly distributedwithin a particle size range of between about 1 and about 2 microns.Such porous polymer bodies exhibit very wide range of B.E.T. surfaceareas, e.g., from 1 to about 1300 m² /g, commonly 500 to 900, mosttypically 700 to 800 m² /g. Pore sizes are in the range of between about100 and about 200 Angstroms. Pore volume is generally in the range ofbetween about 0.2 and about 0.2 cc/g.

Although porous adsorbent materials are preferred for many applications,the adsorbent bodies of the structures of the invention may also beconstituted of substantially non-porous carbon, organic polymer andother nucleophilic materials.

Schematically illustrated in FIG. 2 is a transverse cross section of achromatographic column of the invention. An actual photomicrograph of asegment of this cross section is shown in FIG. 1. Bound to and extendingalong interior wall 3 of a tubular glass column 1 is coating layer 5which comprises a network or webbing of polysiloxane 7 having carbonparticles 9 embedded therein. As contained by the polysiloxane network,the carbon particles are effectively stacked inward of wall 3 in aplurality of layers which may in total thickness range from about 0.2microns to about 1.0 mm, equivalent to as many as fifty effective layersof carbon. Carbon particles are distributed within network 7 bothlaterally and vertically with respect to the surface of wall 3. The--Si--O--Si-- bonds between the polysiloxane webbing and the glass wall,and the .tbd.C--Si.tbd. bonds between the webbing and the carbon arestable at temperatures up to and above 400° C. Moreover, the mechanicalstrength of the bonds prevents carbon from being loosened and entrainedin either a sample matrix or a rinsing fluid. Yet despite the highintegrity of the bonding medium, coating layer 5 is readily permeable toanalytes contained in a sample matrix, so that the carbon surfacesthroughout the coating layer are accessible to the analytes. It isbelieved that coating layer 5 comprises a substantial degree ofporosity, the pores providing tortuous paths for the analyte to transferfrom particle to particle, hence differential adsorption isaccomplished. It is further understood that the polysiloxane webbing ispermeable to Knudsen diffusion of analytes, further augmenting access ofanalytes to the carbon surfaces. In any case, the carbon coatingpresents a very high adsorptive capacity, and provides a very highdegree of resolution per unit of column length.

It will be understood that, as used herein, the term "chromatographiccolumn" does not necessarily denote a vertical column, but encompassesany tube, duct or chamber containing sorbent material over which asample matrix may be passed for purposes of chromatographic separation.

Glass, metal or plastic chromatographic columns of the invention, havingactive carbon coated on the interior walls, may be used in gas/solidchromatography for separating complex sample matrices. The choice ofcarbon is dependent on the nature of sample. Carbon molecular sievesseparate analytes based on molecular size, while other carbon adsorbentseffect separation based on differences in electronic activity among theanalytes. Optionally, selectivities can be substantially enhanced bycoating the carbon particles with liquid stationary phase materials onwhich the relative adsorptivities of analytes, particularly based ontheir electronic activities, vary more sharply than on the carbonitself. The column of the invention allows such gas/liquid/solidchromatography to be conducted with high capacity, minimal axialbackmixing, and low pressure drop. Particularly advantageous liquidstationary phase materials are cyclodextrins, which can readily becoated onto the surface of the bound carbon particles. Alternativelygas/liquid or gas/liquid/solid chromatography can be conducted using aphthalocyanine, or other polar, stationary phase, coated on a carbonsupport that is bonded to the interior column wall in accordance withthe novel compositional structure of the invention. By varying thelayers of liquid phase coated over the carbon, the column function canbe varied from entirely gas/liquid chromatography to varying degrees ofgas/liquid/solid operation. With greater than about five layers ofliquid, the gas adsorptive capability of the carbon is essentiallycompletely masked, and the column functions in a liquid/liquid mode. Asthe number of layers decreases below five, influence of the carbonprogressively increases. Although the cyclodextrin or phthalocyanine isare bound to the carbon only by Van der Waals forces, strong bonding ofthe carbon to the glass or other column wall surface via thepolysiloxane prevents both the carbon and the liquid phase it supportsfrom being swept out of the column by a flowing gas sample matrix, evenwhen multiple liquid layers are used. It will be understood that bysubstitution of a liquid mobile phase, columns constructed according tothe invention can be operated in a liquid/liquid mode as well, and thatthe strong bond between the carbon support and the glass surfaceprevents entrainment of carbon in the liquid mobile phase.

Columns of the invention coated with zeolite molecular sieve, activatedalumina, activated silica, silica gel and adsorbent organic polymers viaa polysiloxane adhesive also may be advantageously used in gas/solidchromatography applications. Separations are primarily effected on asize exclusion principle, but other mechanisms of differentialadsorption may be implemented in such columns. As in the case of carbon,adsorbent bodies comprising silica, alumina, zeolite, organic polymerand other adsorbent materials may function as supports for a stationaryliquid phase in reversed phase gas/liquid or liquid/liquidchromatography. The liquid phase may be adhered to the surface of theadsorbent body by Van der Waals forces only or, alternatively, thesupport may be derivatized by having materials chemically bonded theretowhich present a stationary liquid surface for contact with a mobileliquid or gas phase. Thus, for example, silica that is bonded to a glassor metal substrate via a polysiloxane polymer, may be derivatized byattachment of aliphatic moieties thereto, such as octadecyl radicals.

In accordance with the chromatographic method of the invention, a samplematrix mobile phase containing one or more analytes is passed through acoated wall column of metal, plastic or vitreous material. A preferredsubstrate material is silica glass. The walls of the column are coatedwith adsorbent carbon, zeolite, alumina, silica, or organic polymer,which is bound to the substrate via a polysiloxane polymer, in themanner described hereinabove. Preferably, the column is of capillarydiameter, i.e., typically between about 0.1 and about 1 mm. Thus, thechromatographic column of the invention is adapted for use in PLOT,SCOT, CLOT or GLOT form. Columns of capillary diameter may contain acarbon coating of small enough particle size and high enough loading topresent an adsorptive area of between about 1 and about 12 m² per m ofcolumn length, or between about 600 and about 7250 cm² per cm² ofinternal wall surface, for a column internally coated with a singlecarbon layer. For other adsorptive materials, the ranges of adsorptivearea are as set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                                   B.E.T. Surface Area per                                                         Unit col. length                                                                          Unit col. Area                                       Adsorbent Mat'l                                                                            m.sup.2 /m  cm.sup.2 /cm.sup.2                                   ______________________________________                                        Zeolite      1-10        500-10,000                                           Alumina      1-40        300-10,000                                           Silica       1-12        300-10,000                                           Org. Polymer 1-12        300-10,000                                           ______________________________________                                    

By use of multiple coatings, the absorptive capacity can besubstantially increased without significant increase in pressure drop.For example, a column having fifty C/siloxane layers on the internalwall may present an adsorptive area of between about 1 and about 600 m²per m of column length, or between about 600 and about 375,000 cm² percm² of internal wall surface. Such adsorptive area is provided, forexample, by carbon having a particle size of between about 0.5 and about10 μM, and a B.E.T. surface area of between about 1 and about 1500 m²/g, at coating thickness of between about 0.5 and about 1 mm and aloading of between about 0.001 and about 0.600 g/cm² of internal wallsurface. Typically the total weight of carbon in a capillary column isin the range of between about 1.0 mg and about 10 g.

In the case of a zeolite molecular sieve having a particle size betweenabout 0.5 and about 10 microns, B.E.T. surface area of between about 200and about 800 m² /g, a coating thickness of between about 0.5 and about500 μm and a loading of between about 0.001 and about 1.0 g/cm², acolumn having fifty zeolite/siloxane layers on the internal wall of acolumn may present an adsorptive area of between about 1 and about 400m² per m of column length, or between about 500 and about 10,000 cm² percm² of internal wall surface. For fifty layers of other adsorbent bodiesembedded in a polysiloxane, the comparable ranges for:

(a) alumina are a particle size between about 0.5 and about 10 microns,a B.E.T. surface area of between about 200 and about 800 m² /g, acoating thickness of between about 0.5 and about 500 μm and a loading ofbetween about 0.001 and about 1.0 g/cm², to provide an adsorptive areaof between about 1 and about 10m² per m of column length, or betweenabout 300 and about 300,000 cm² per cm² of internal wall surface;

(b) for activated silica are a particular size between about 0.5 andabout 10 microns, a B.E.T. surface area of between about 5.0 and about1000 m² /g, a coating thickness of between about 0.5 and about 500 μmand a loading of between about 0.001 and about 0.6 g/cm², to provide anadsorptive area of between about 1 and about 12 m² per m of columnlength, or between about 500 and about 10,000 cm² per cm² of internalwall surface;

(c) for silica gel are a particle size between about 0.5 and about 10microns a B.E.T. surface area of between about 5 and about 1200 m² /g, acoating thickness of between about 0.5 and about 500 μm and a loading ofbetween about 0.001 and about 0.6 g/cm ², to provide an adsorptive areaof between about 1 and about 12 m² per m of column length, or betweenabout 600 and about 7250 cm² per cm² of internal wall surface;

(d) for a styrene-divinylbenzene copolymer are a particle size betweenabout 1 and about 10 microns, a B.E.T. surface area of between about 1and about 1200 m² /g, a coating thickness of between about 0.5 and about500 μm and a loading of between about 0.001 and about 10 g/cm², toprovide an adsorptive area of between about 1 and about 12 m² per m ofcolumn length, or between about 600 and about 7250 cm² per cm² ofinternal wall surface; and

(e) for a polymethacrylate ester polymer are a particle size betweenabout 1 and about 10 microns, a B.E.T. surface area of between about 1and about 1200 m² /g, a coating thickness of between about 0.5 and about500 μm and a loading of between about 0.001 and about 12 g/cm², toprovide an adsorptive area of between about 1 and about 12 m² per m ofcolumn length, or between about 500 and about 7250 cm² per cm² ofinternal wall surface.

In each case, the total weight of adsorbent bodies on the wall of acapillary column is comparable to that noted above in the case ofcarbon, i.e., roughly about 0.1 to about 10 g.

Chromatographic columns of the invention can be used in chromatographicanalyses, or other chromatographic separations, of an essentiallyunlimited variety of mixtures. According to the chromatographic processof the invention, a mixture to be analyzed or otherwise separated isintroduced into the column, and components of the mixture are elutedfrom the column using a liquid solvent or carrier gas. It isparticularly preferred that the column be an open column such as thePLOT, SCOT, CLOT or GLOT columns described hereinabove. In gaschromatography, the column of the invention has been demonstrated to besuitable for such exemplary applications as the separation of: varioushydrocarbon gases; combustion gases; aqueous solutions of nonionicsolutes; and light sulfur gases. It is particularly effective for use inseparation and analysis of flue gases obtained from the combustion ofsulfur-bearing fuels, and light sulfur gases of the type that may bereleased from crude petroleum or sour petroleum fractions. Advantageousapplications particularly include the separation and analysis ofmixtures comprising sulfur bearing carbon compounds having boilingpoints below about 22° C. at atmosphere pressure. The chromatographiccolumns of the invention are further suited for separation and analysisof internal combustion engine exhaust gases and other gases which maycontain significant fractions of oxides of nitrogen, oxides of sulfur orboth. The conditions for conducting these and other analyses andseparations are not narrowly critical. However, the separation mechanismof porous carbon, zeolite, alumina, silica or organic polymer PLOTcolumns is typically one of molecular size and shape, and in someparallel instances becomes one of boiling point of the introducedanalytes. For these reasons, the porosity and/or specific surface areaof the adsorbent body may play a major role in the separationcharacteristics of such PLOT columns. More particularly, the particulatecarbon used in a size exclusion PLOT column preferably has a pore volumeof about 1.5 to about 2.0 cc/g and a B.E.T. surface area of betweenabout 400 and about 1300 m² /g, preferably between about 700 and about800 m² /g. Comparable parameters for other adsorbent materials are setforth in Table 2.

                  TABLE 2                                                         ______________________________________                                        Preferred Characteristics of Adsorbent                                        Materials Used for Size Exclusion                                             Separation - PLOT Column                                                      Adsorbent    Pore      B.E.T.  Preferred                                      Material     Vol.      Area    B.E.T. area                                    ______________________________________                                        Zeolite      0.40      350     350                                            Alumina      0.45      250     200                                            Act. silica  1.50      300     350                                            Silica gel   1.50      500     7000                                           DVB          1.25      350     750                                            Polymethacrylate                                                                           0.20      250     500                                            ______________________________________                                    

In other applications, such as, for example, the separation of complexenvironmental mixtures such as chlorinated compounds present in drinkingwater, waste effluent streams, and hazardous waste sites, relatively lowporosity graphitic carbons may be used. Graphitic carbons can also beused in analyses of halofluorocarbons ("Freons") typically used inrefrigerant systems. Substantially non-porous carbons useful in certainof these applications have a B.E.T. surface area generally less than 100m² /g, while slightly porous graphitic carbons generally have a B.E.T.surface area in the range of about 250 m² /g and about 500 m² /g.

Using open columns of the type described above, the separation processcan be operated at very modest pressure drop, e.g., in the range of 0.1to 100 psi, more commonly in the range of between about 2 and about 30psi. Exemplary conditions are illustrated in the working examples setforth hereinbelow. Acceptable variations in these conditions will bereadily apparent to those skilled in the art.

Columns that are interiorly coated with carbon or other adsorbentparticles in accordance with the invention can be used in samplepreparation applications also. When sample matrices contain impuritieswhich are not to be analyzed, but whose presence can interfere with thedetermination of analytes of interest, it is desirable or necessary toremove the impurities before chromatographic analysis is begun. One wayin which impurities may be removed is to cause the sample to flowthrough a column containing an adsorptive material which has a strongeraffinity for the impurities than for the analytes. Carbon molecularsieves, porous carbons, activated porous carbons, zeolites, activatedalumina, silica, silica gel, and porous organic polymers are especiallysuitable for this purpose. By use of a coated wall column of theinvention for sample preparation, the sample may be processed rapidly,with low pressure drop, and with high selectivity so that impurities arequantitatively removed while the loss of analyte during samplepreparation is carefully and reliably avoided.

Illustrated in FIG. 3 is a solid phase extraction device which comprisesa syringe barrel 101 containing a coated glass fiber 103 which can beexposed for immersion in a sample matrix by moving it out of the barrelthrough a septum 105 in exit port 107 of the barrel. The inner end offiber 103 connects to a plunger 109 via a screw hub 111. Plunger 105 istelescoped within barrel 101 at the end of the barrel opposite port 107,for slideable axial movement relative to the barrel while in sealingengagement with the interior wall thereof. A ferrule 113 attached to theend of the barrel surrounding port 107 holds a septum piercing hollowneedle 115. Needle 115 is aligned with fiber 103 so that the fiber maybe passed axially through the interior of the needle. Thus, by pressingdown on the plunger, the fiber may be moved axially of the barrel andout through septum 105 and needle 115, for immersion into a samplematrix and adsorption of an analyte, or contaminant, or componentcontained within the matrix. After the adsorption of such component,fiber 103 is conveniently withdrawn back into the barrel until such timeas the adsorbed component is to be desorbed into another matrix, forexample, into the mobile phase of a chromatographic separation system.By then depressing the plunger the fiber 103 may be forced out of thebarrel and into a sample matrix, or into the injection port of achromatographic column.

Fiber 103 is coated with fine particles 117 of carbon or other adsorbentmaterial which are bound to the glass surface via siloxane polymers inthe manner described hereinabove. FIG. 4 shows a cross section of one ofthe fibers of the solid phase extraction device of FIG. 3. From FIG. 4it may be seen that the adsorbent particles are embedded in a network orwebbing 119 of polysiloxane on the outside of the fiber and extendingalong thereof. This webbing is comparable to the webbing 7 ofpolysiloxane on the inside surface of the tubular wall of thechromatographic column illustrated in FIGS. 1 and 2. The single fiber103 having a length, for example, of 0.1 m, may comprise an activesurface area of between about 1 and about 1.2 m², using adsorbent bodieshaving the B.E.T. surface area discussed hereinabove.

When the device of FIGS. 3 and 4 is immersed in a sample matrix,analytes or impurities having an affinity for the carbon are adsorbedthereon, and thus removed from the sample matrix. In this manner, forexample, impurities may be removed from a matrix, which then may besubjected to chromatography or other analysis. Alternatively, analytesof interest may be removed from the sample matrix, then transferred fromthe carbon or other adsorbent particle surface to another sample matrix,free of impurities that may contaminate the first matrix. If desired amore concentrated sample solution may be prepared in this fashion, usinga much lower volume of eluting solvent than would be required in acolumn type extraction device, and orders of magnitude less solvent thanwould be required using conventional liquid/liquid extractiontechniques. Access of analyte to the carbon or other adsorbent particlesembedded in webbing 119 is realized in essentially the same manner as inthe case of the webbing 7 of the chromatographic column of FIG. 1.Samples of analytes that have been concentrated or purified by solidphase extraction may then be subjected to further analysis bychromatography or other means.

The novel structures of the invention may be embodied in other forms ofseparation devices. For example, the adsorbent bodies may be adhered viaa siloxane polymer to the fibers of a woven or blown fiber fabric.Conveniently, such fabric may be cut or formed in the shape of a disk,through which a matrix solvent containing analytes to be removed arepassed orthogonally to the surface of the fabric. If desired, a solidphase extraction device may comprise a multiplicity of layers of suchfabrics, e.g., in the form of stacked disks as shown in U.S. Pat. No.5,279,742, the disclosure of which is incorporated herein by reference.In such a device, the matrix solution is passed sequentially through thestacked disks of fabric, which may each contain the same adsorbentmaterial, or which may contain different adsorbent materials that areeffective for adsorption of different analytes. The latter arrangementmay be advantageously used for separation of a plurality of analytes inthe sample by physical separation and separate elution of the disks.However, it should be noted that a particular advantage of the novelstructures of the invention arises from the strong adsorptive power andlarge adsorptive capacity made possible by the secure adherence of ahigh concentration of adsorbent bodies to a fiber substrate. Thus,unlike certain of the stacked disk systems of the prior art, multiplefabric layers are not usually necessary to effect separation of a singleanalyte. Nonetheless, the stacked disk arrangement may be effectivelyused in the manner described herein for definitive and quantitativeseparation of different analytes.

In preparation of the adsorbent filter of the invention, a solution ofsiloxane polymer is prepared in a suitable solvent, and the adsorbentparticles suspended in the resultant solution, in the manner essentiallyas described above. The suspension is drawn into a graduated/calibratedpipette and then discharged from the pipette over the top of a fiberfilter to provide an even coating over the filter. The filter isthereafter placed in a vacuum-drying oven and dried under vacuum orinert gas at a temperature in the range described above as effective forreaction of the hydrosiloxane polymer with the nucleophilic compositionof the adsorbent particles, generally >150° C. If the filter walls orfibers are of a plastic material such as polypropylene or polyethylene,drying and reaction of the polysiloxane with the substrate and theadsorbent bodies is preferably conducted at a temperature between about100° C. and about 150° C.

The structures of the invention are also useful in a variety of otherdifferential adsorption separation devices. For example, illustrated inFIG. 9 is a denuder device that is useful in removing contaminants froman air sample. The denuder comprises a glass, plastic or metal tube 201having adsorbent particles 203, typically of carbon or MgO, bound to theinterior wall 205 of the tube via a polysiloxane polymer medium 207. Agas sample enters the tube through an inlet nipple 209, and exitsthrough an exit nipple 211. In an alternative structure as illustratedin FIG. 10, the denuder comprises a plurality of parallel tubes 301secured in tube sheets 311 and 313, and having adsorbent particles 303bound to the interior walls 305 of the tubes via polysiloxane. Samplegas enters the tubes through an inlet head 307 and exits the tubes via adischarge head 309. The structure of FIG. 10 provides an enhancedadsorptive surface area as compared to the denuder of FIG. 9.

Such devices may be used upstream of a glass or Teflon fiber filter usedto collect particulates from an air sample in a determination ofparticulate concentration. For example, nitric acid in the air may beremoved by adsorption on the carbon or MgO, thus eliminating an artifactthat may otherwise be encountered in the analysis of the air sample fornitrate-bearing particulates. The denuder of the invention may beadvantageously used, for example, in the method and apparatus describedin Shaw, et al., "Measurements of Atmospheric Nitrate and Nitric Acid;the Denuder Difference Experiment," Atmospheric Environment, Vol. 16,No. 4, pp. 845-853 (1962); and in Stevens and Dzubay, "Sampling ofAtmospheric Sulfates and Related Species," Atmospheric Environment, Vol.12, pp. 55-68 describes another denuder apparatus and applicationthereof.

It has further been found that the structure of the invention may beusefully embodied in a catalytic reactor in which a catalyst is bondedto a wall of the reactor via a polysiloxane adhesive. Essentially anymetal or ceramic wall having a nucleophilic surface composition may beused as the substrate for the polysiloxane bound catalyst. The catalystmay be any catalyst having a surface composition sufficientlynucleophilic for reaction with silyl hydride moieties of the siloxanepolymer.

Although it is preferred for many applications to adhere the bodies ofnucleophilic material to the substrate by bonding through the silylhydride groups of a hydrosiloxane polymer, it has been found that, inthe alternative, the bonding reaction with the polysiloxane may beeffected through the silyl halide functionality of a halosiloxanepolymer. Substrate materials may also react with a silyl halide ratherthan a silyl hydride. Where the material of the substrate or particulatematerial is a glass, metal, alumina, silica, zeolite, or the like, thebond between that material and siloxane is via an oxygen linkage, e.g.,Si--O--Si, Si--O--Al, or Si--O--M (where M=metal), regardless of whetherthat material reacts with a silyl hydride or silyl halide group. Carbonand organic polymers react with either a silyl hydride or silyl halideto produce a direct .tbd.C--Si.tbd. bond.

In bonding bodies of nucleophilic composition to the surface of avitreous or other substrate, the substrate surface is contacted with amixture of the halosiloxane polymer, and a granular or particulatezeolite, alumina, silica, organic polymer, elemental carbon or othernucleophilic material, and the mixture heated to cause the siloxanepolymer to be bonded to the particles by and to the substrate. To carryout this process, the halosiloxane polymer is preferably dissolved in asuitable solvent, the granular or particulate slurried in the solution,and the substrate contacted with the slurry and heated to effect thereaction. The halosiloxane polymer has the structure: ##STR12## where Xis halogen, R, R²³, R²⁴, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹ and R⁺ areindependently selected from among substituted and unsubstitutedhydrocarbyl, nitro, cyano, halo and an --O--Si.tbd. moiety, m+n is suchthat the molecular weight of the polymer is between about 80,000 andabout 2 million, and m/(m+n) is between about 0.01 and about 1.0, morepreferably between about 0.02 and about 0.2. Where any of R, R²³, R²⁴,R²⁵, R²⁶, R²⁷, R²⁸, R²⁹ and R⁺ is hydrocarbyl, it may be any of thegroups that may constitute R in Formula II. Where any of R, R²³, R²⁴,R²⁵, R²⁶, R²⁷, R²⁸, R²⁹ and R³⁰ is --O--Si.tbd., it advantageouslyconstitutes the residue of a surface silanol residue of a vitreoussubstrate, thus serving as a bridge between the substrate and thesiloxane polymer. Alternatively, a branched polysiloxane may be used,comparable to the type represented by Formula VA or Formula V wherein Rcomprises Formula IX, but containing a halogen substituent in place ofthe hydrogen substituent at the point of reaction between the siloxaneand the carbon surface.

Although carbon bodies are preferably deoxygenated prior to reactionwith either a hydrosiloxane or halosiloxane polymer, carbon bodieshaving surface .tbd.C--OH functionality may also be used, in which casethe attachment is via a .tbd.C--O--Si.tbd. linkage. In the latterinstance, the composition of the bonding means corresponds to theformula: ##STR13## where R is as defined above. Although its thermalstability is not as great as that of the direct C--Si bond, the C--O--Sibond nonetheless comprises a means for bonding the carbon particles tothe glass whose integrity is substantially superior to that of the Vander Waals type bonding agents that have been conventionally used in theart. In this embodiment of the invention, a siloxane polymer comprisinga silyl hydride and/or silyl halide functionality is reacted with carbonparticles having residual bound oxygen or hydroxyl groups on the surfacethereof: ##STR14## where each of X¹ and X² is either hydrogen orhalogen.

For purposes of this reaction, a carbon surface is advantageouslyprepared to introduce bound oxygen or hydroxyl groups. This may beeffected, for example, by contacting the surface with an oxidizing agentsuch as nitric acid or an oxidizing plasma, e.g., a plasma comprising anoxidized organic monomer such as benzylic acid.

It will be understood that the siloxane polymer may comprise both silylhydride and silyl halide, typically silyl chloride or silyl bromide,functionality, and that the substrate may react with one functionalgroup, the particulate, granular or fibrous bodies may react with theother functional group, or both functionalities may react with bothsubstrate and the discrete bodies. The discrete bodies may serve any ofa large variety of functions. As noted, they may constitute theadsorbent bodies of a chromatographic column or solid phase extractionapparatus, or they may comprise a solid phase catalyst bound to the wallof a tubular reactor. In chromatographic, solid phase extraction andcatalytic applications, the bodies are ordinarily comprised of adsorbentmaterial. In many but not all instances, the adsorbent material isporous, preferably comprising a high degree of porosity and asubstantial B.E.T. surface area as described above.

Where the invention is embodied in a chromatographic apparatus or solidphase adsorption device, discrete adsorbent bodies are typically bondedto a monolithic or essentially monolithic substrate, such as an interiorwall of a chromatographic column, or a fiber or contiguous network offibers that support the adsorbent particles of a solid phase adsorptiondevice. As used herein, the term "monolithic" includes essentiallymonolithic structures such as a weave or mat of contiguous fibers.

In certain applications known to the art, a particulate substrate mayprovide desirable functions or advantages. It will be understood that,in certain embodiments, the novel chromatographic apparatus or solidphase adsorption device of the invention may comprise a substrate whichitself comprises discrete bodies, to which discrete adsorbent bodies arebonded with a siloxane polymer. There may also be applications otherthan in chromatography, sample preparation, or catalysis whereindiscrete bodies having a functional surface property are bonded to amonolithic or particulate substrate via the medium of a siloxanepolymer.

While the emphasis of the above disclosure has been on discrete bodieswhich are adsorbent, or preferably porous, it will be understood thatthe compositions and structures of the invention are further applicableto the bonding to substrates of other bodies of nucleophilic materialthat may be non-porous and/or non-adsorbent and/or not discrete. In thefield of chromatography for example, a plug of fibrous material, such asrock wool, may be adhered to the interior wall of a column via asiloxane polymer to provide support for a packed bed of particulate orgranular adsorbent material that comprises the stationary phase of achromatographic system.

To produce a packed column in which the packing is secured by rock woolend plugs, a plug is force fit into the one end of the column andpacking introduced. If plug is used at the other end of the column, itis force fit into that end after the packing is in place. Thereafter, asolution of a siloxane polymer, preferably a hydrosiloxane polymer, in asuitable solvent (such as dichloromethane) is dispensed into each end ofthe column that contains a wool plug. The column ends are then insertedinto a suitable heating device to effect bonding of the silyl hydride(or silyl halide) functionality of the siloxane polymer to the interiorwall of the column. The temperatures required for the reaction are asdiscussed above.

The following examples illustrate the invention.

EXAMPLE 1

Dichloromethane (2.0 mL) was mixed with a polymethylhydro-dimethylsiloxane glue having a molecular weight of 210,000 Daltons, in which 5%of R¹ to R⁹ are hydrogen, the remainder of R¹ to R⁹ are methyl, andm/(m+n) is 0.5 (80 mg), and the resulting mixture was sonicated forapproximately 1.0 hours to dissolve the siloxane in the solvent.Particulate carbon (120 mg) sold under the trade designation Carboxen1006 by Supelco, Inc. was weighed out into a separate vial, and thesolution of siloxane in dichloromethane added to the vial containing thecarbon. Carboxen 1006 has a particle size of 0.4 to 0.5 μM, a B.E.T.surface area of 750 m² /g, a total pore volume of 15 cc/g, a macroporevolume of 0.5 cc/g, a mesopore volume of 0.5 cc/g a micropore volume of0.5 cc/g and a density of 0.44 g/cc. The resulting slurry was sonicatedfor 2.0 hours to uniformly suspend the carbon in the solution. Thesonicated slurry was then transferred to a reservoir for use inproviding a porous layer coating on the inside wall of a tubular fusedsilica column having an I.D. of 0.53 mm and a length of 30 meters.

A flow of N₂ was established in the column at a pressure ofapproximately 20 psig and the slurry of carbon in siloxane solutionflowed by gravity and N₂ pressure through the column from the reservoir.The suspension was allowed to pass entirely through the column,providing a coating of carbon in siloxane on the internal glass wall.Effluent siloxane suspension was collected in a dispensing vial. Afterdrainage of the effluent had substantially ceased, the column was placedin an oven, and heated at 260° C. for about 10 minutes under a N₂ purgeat a pressure of about 5 psig. Reaction of the siloxane polymer withboth the carbon and the glass resulted in a carbon coating on theinterior surface of the column which was strongly bonded to the fusedsilica glass via a webbing of the siloxane.

This procedure was repeated multiple times to provide a column havingmultiple layers of carbon bound to and embedded in a porous siloxanepolymer webbing that was in turn bonded to the glass. A photomicrographof a cross-section of the resulting column is set forth in FIG. 1.

EXAMPLE 2

Using the column prepared in the manner described in Example 1, amixture of gas containing carbon monoxide, carbon dioxide, methane,ethane, ethylene, and acetylene in bulk nitrogen was subjected tochromatographic separation. The sample was injected at the column inletand caused to flow through the column by a mobile phase comprisinghelium. The helium eluent was passed through the column at a flow rateof 3.00 mL/min. During elution, the column temperature was initiallymaintained at 35° C. for three minutes, then ramped up to 225° C. at aheating rate of 24° C. per minute. Column pressure was initially 4 psig,increasing to 6 psig at the elevated temperature. Bands of components ofthe mixture exiting the column were analyzed by a thermal conductivity(i.e., hot wire) detector upon elution. The resulting chromatogram isset forth in FIG. 5. Integration of the peaks appearing in FIG. 5provided the analysis of the mixture set forth in Table 1. As indicatedby peak width, the efficiency of the column was approximately threetimes that of a conventional packed carbon column. As measured by carbondioxide equilibria, the column contained the equivalent of 12,524equilibrium stages.

                  TABLE 1                                                         ______________________________________                                        #    COMPONENT    AREA %      RT   AREA BC                                    ______________________________________                                        1    Nitrogen     9.829       2.81 611277 02                                  2    Nitrogen     32.56       2.9  2024922 02                                 3    Nitrogen     51.648      2.9  3212010 02                                 4    Carbon Monoxide                                                                            1.166       3.21 72484 03                                   5    Methane      0.679       4.78 42205 01                                   6    Carbon Dioxide                                                                             1.099       6.66 68371 01                                   7    Acetylene    0.867       8.45 53917 01                                   8    Ethylene     1.045       9.56 64963 01                                   9    Ethane       1.108       10.33                                                                              68902 01                                   ______________________________________                                    

EXAMPLE 3

Using a column of the type prepared in Example 1, a specimen of ethylenegas was analyzed for trace quantities of acetylene. The analysis wasconducted generally in the manner described in Example 2. Helium eluentwas passed through the column at a flow rate of 3.00 mL/min. The columntemperature was maintained at 165° C. during elution. Column pressurewas 6.0 psig. The resulting chromatogram is set forth in FIG. 6.

EXAMPLE 4

Using a column of the type prepared in Example 1, a formalin solutionwas analyzed for water, formaldehyde and methanol content. The analysiswas conducted generally in the manner described in Example 2. Heliumeluent was passed through the column at a flow rate of 3.00 mL/min.Elution was carried out isothermally at a temperature of 220° C. Thepressure in the column was 8.0 psig. The resulting chromatogram is setforth in FIG. 7.

EXAMPLE 5

Using the method generally described in Example 2, a light sulfur gasmixture was analyzed using a PLOT column similar to that described inExample 1. Dimensions of the column were 0.53 mm I.D. ×15 meters inlength. During elution, the temperature was held at 50° C. for oneminute, then ramped to 250° C. at a rate of 24° C./min. Helium waspassed through the column at a flow rate of 3.0 mL/min, and the pressurewas observed to rise from 3.0 psig at 50° C. to 10.0 psig at 250° C. Theresulting chromatogram is set forth in FIG. 8.

EXAMPLE 6

Dichloromethane (2.0 mL) was mixed with a polymethylhydro-dimethylsiloxane glue having molecular weight of 200,000 Daltons, in which 5% ofR¹ to R⁹ are hydrogen, the remainder of R¹ to R⁹ are methyl and m/(m+n)is 0.5 (80 mg), and the resulting mixture was sonicated forapproximately 2.0 hours to dissolve the siloxane in the solvent. Aparticulate zeolite molecular sieve (150 mg) was weighed out into aseparate vial, and the solution of siloxane in dichloromethane was addedto the vial containing the zeolite. The resulting slurry was sonicatedfor 1.0 hours to uniformly suspend the zeolite in the solution. Thesonicated slurry was then transferred to a reservoir for use inproviding a porous layer coating on the inside wall of the tubular glasscolumn having an I.D. of 0.53 mm and a length of 30 meters.

A flow of nitrogen was established in the column at a pressure ofapproximately 30 psig and the slurry of zeolite in siloxane solutionflowed by gravity and nitrogen pressure through the column from thereservoir. The suspension was allowed to pass entirely through thecolumn, providing a coating of zeolite in siloxane on the internal glasswall. Effluent siloxane suspension was collected in a dispensing vial.After drainage of the effluent had substantially ceased, the column wasplaced in an oven and heated at 260° C. for about 10 minutes under anitrogen purge at a pressure of about 20 psig. Reaction of the siloxanepolymer with both the zeolite and the glass resulted in a zeolitecoating on the interior surface of the column which was strongly bondedto the glass via a webbing of the siloxane.

This procedure was repeated multiple times to provide a column havingmultiple layers of zeolite particles bound to and embedded in a poroussiloxane polymer webbing that was in turn bonded to the glass.

EXAMPLE 7

Using the column prepared in the manner described in Example 6, a gasmixture containing oxygen, argon, nitrogen, methane, carbon monoxide,and carbon dioxide was subjected to chromatographic separation. Thesample was injected at the column inlet and caused to flow through thecolumn by a mobile phase comprising helium. The helium eluent was passedthrough the column at a flow rate of 3.0 mL per minute. During elution,the column was maintained at a temperature of 35° C. and a pressure of2.0 psig. Bands of components of the mixture exiting the column wereanalyzed by a thermal conductivity (i.e., hot wire) detector uponelution. The resulting chromatogram is set forth in FIG. 11.

EXAMPLE 8

Using a zeolite column of the type prepared in Example 6, room air wassubjected to chromatographic analysis. The eluent was helium, passedthrough the column at a flow of 3.0 mL per minute. Elution was conductedat a temperature of 35° C. and 2.0 psig. Analysis was by thermalconductivity. The resulting chromatograph is set forth in FIG. 12.

EXAMPLE 9

Dichloromethane (2.0 mL) was mixed with a polymethylhydro-dimethylsiloxane glue having molecular weight of 210,000 Daltons, in which 5% ofR¹ to R⁹ are hydrogen, the remainder of R¹ to R⁹ are methyl and m/(m+n)is 0.5 (60 mg), and the resulting mixture was sonicated forapproximately 20 hours to dissolve the siloxane in the solvent.Particulate styrene-divinylbenzene polymer of the type sold under thetrade designation SUPELPAK™ by Supelco, Inc. of Bellefonte, Pennsylvania(60 mg) was weighed out into a separate vial, and the solution ofsiloxane in dichloromethane added to the vial containing thestyrene-divinylbenzene polymer. The resulting slurry was sonicated for1.0 hours to uniformly suspend the porous polymer in the solution. Thesonicated slurry was then transferred to a reservoir for use inproviding a porous polymer layer coating on the inside wall of a tubularglass column having an I.D. of 0.53 mm and a length of 30 meters.

A flow of nitrogen was established in the column at a pressure ofapproximately 30 psig and the slurry of styrene-divinylbenzene copolymerin the siloxane solution flowed by gravity and nitrogen pressure throughthe column from the reservoir. The suspension was allowed to passentirely through the column providing a coating of porousstyrene-divinylbenzene copolymer in siloxane on the internal glass wall.Effluent siloxane suspension was collected in a dispensing vial. Afterdrainage of the effluent had substantially ceased, the column was placedin an oven, and heated at 260° C. for about 10 minutes under a nitrogenpurge at a pressure of about 20 psig. Reaction of the siloxane polymerwith both the styrene-divinylbenzene polymer and the glass resulted in aporous polymer coating on the interior surface of the column which wasstrongly bonded to the glass via a webbing of the siloxane.

This procedure was repeated multiple times to provide a column havingmultiple layers of porous styrene-divinylbenzene polymer bound to anembedded in a porous siloxane polymer webbing that was in turn boundedto the glass.

EXAMPLE 10

Using the column prepared in the manner described in Example 9, a gasmixture comprising carbon dioxide and gasoline vapor was subjected tochromatographic separation. The sample was injected at the column inletand caused to flow through the column by mobile phase comprising helium.The helium eluent was passed through the column at a flow rate of 3.0 mLper minute. Elution was conducted at a temperature of 35°-250° C. and apressure of 3.0 to 15 psig. Bands of components of the mixture exitingthe column were analyzed by a thermal conductivity detector uponelution. The resulting chromatogram is set forth in FIG. 13.

EXAMPLE 11

Using a column of the type prepared in Example 9, a gas mixturecomprising carbon dioxide and C₄ hydrocarbons was subjected tochromatographic separation. The analysis was conducted generally in themanner described in Example 10. helium eluent was passed through thecolumn at a flow rate of 3.0 mL per minute. The elution was conducted at35° C. to 150° C. and 2.0-10.0 psig. The resulting chromatogram is setforth in FIG. 14.

EXAMPLE 12

Using the column prepared in the manner described in Example 9, a gasmixture comprising vaporized jet fuel No. 4 was subjected tochromatographic separation. The analysis was conducted generally in themanner described in Example 10. Helium eluent was passed through thecolumn at a flow rate of 3.0 mL/min. The column was operated at atemperature of 35°-2000° C. and a pressure of 3.0-75 psig during theelution. The resulting chromatogram is set forth in FIG. 15.

EXAMPLE 13

Using the column prepared in the manner described in Example 9, carbondioxide and vaporized jet fuel No. 4 was subjected to chromatographicseparation. The analysis was conducted generally in the manner describedin Example 10. Helium eluent was passed through the column at a flowrate of 3.0 mL/min. The column was operated at a temperature of 35° C.to 250° C. and a pressure of 2.0-15 psig during the elution. Theresulting chromatogram is set forth in FIG. 16.

EXAMPLE 14

Using the column prepared in the manner described in Example 9, a gasmixture comprising C₃ alcohol vapors was subjected to chromatographicseparation. The analysis was conducted generally in the manner describedin Example 10. Helium eluent was passed through the column at a flowrate of 3.0 mL/min. The column was operated at a temperature of 35° C.to 140° C. and a pressure of 3.0-14 psig during the elution. Theresulting chromatogram is set forth in FIG. 17.

EXAMPLE 15

Using the column prepared in the manner described in Example 9, a gasmixture containing permanent gases (air), C₃ hydrocarbons and C₄hydrocarbons was subjected to chromatographic separation. The analysiswas conducted generally in the manner described in Example 10. Heliumeluent was passed through the column at a flow rate of 3.0 mL/min. Thecolumn was operated at a temperature of 35° C. and a pressure of 2.0-15psig during the elution. The resulting chromatogram is set forth in FIG.18.

EXAMPLE 16

Tetrahydrofuran (2.0 mL) was mixed with a polymethylhydro-dimethylsiloxane glue having a molecular weight of 210,000 Daltons, in which 5%of R¹ to R⁹ are hydrogen, the remainder of R¹ to R⁹ are methyl, andm/(m+n) is 0.5 (80 mg), and the resulting mixture was sonicated forapproximately 2.0 hours to dissolve the siloxane in the solvent.Particulate activated alumina (80 mg) was weighed out into a separatevial, and the solution of siloxane and THF added to the vial containingthe activated alumina. The resulting slurry was sonicated for 2.0 hoursto uniformly suspend the alumina in the solution. The sonicated slurrywas then transferred to a reservoir for use in providing a porous layercoating on the inside wall of the tubular glass column having an I.D. of0.53 μm and a length of 30 meters.

A flow of nitrogen was established in the column at a pressure ofapproximately 30 psig and the slurry of alumina in siloxane solutionflowed by gravity and nitrogen pressure through the column from thereservoir. The suspension was allowed to pass entirely through thecolumn providing a coating of alumina in siloxane on the internal glasswall. The effluent siloxane suspension was collected in the dispensingvial. After drainage of the effluent had substantially ceased, thecolumn was placed in an oven and heated at 260° C. for about 10 minutesunder a nitrogen purge at a pressure of about 20 psig. Reaction of thesiloxane polymer with both the alumina and the glass resulted in analumina coating on the interior surface of the column which was stronglybonded to the glass via a webbing of the siloxane.

This procedure was repeated multiple times to provide a column havingmultiple layers of alumina bound to and embedded in a porous siloxanepolymer webbing that was in turn bonded to the glass.

EXAMPLE 17

Using the column prepared in the manner described in Example 16, a gasmixture comprising C₄ hydrocarbons was subjected to chromatographicseparation. The sample was injected at the column inlet and caused toflow through the column by a mobile phase comprising helium. The heliumeluent was passed through the column at a flow rate of 3.0 mL perminute. During elution, the column temperature and was at 35°-250° C.and the pressure at 3.0-20 psig. Bands of components of the mixtureexiting the column were analyzed by a thermal conductivity detector uponelution. The resulting chromatogram is set forth in FIG. 19.

What is claimed is:
 1. A structure comprising discrete adsorbent bodiesbonded to a monolithic substrate through a medium comprising apolysiloxane polymer.
 2. A structure as set forth in claim 1 comprisinga chromatographic apparatus comprising a column having adsorbent bodiesbonded to an interior wall thereof through a medium comprising asiloxane polymer.
 3. A chromatographic apparatus as set forth in claim 2comprising a porous layer open tubular column.
 4. A chromatographicapparatus as set forth in claim 2 comprising a gas chromatograph.
 5. Achromatographic apparatus as set forth in claim 2 comprising a liquidchromatograph.
 6. A chromatographic apparatus comprising a columncontaining a substrate having adsorbent bodies bonded thereto through amedium comprising a siloxane polymer, said bodies comprising anucleophilic composition selected from the group consisting of amorphouscarbon, graphite, turbostatic carbon, zeolite, alumina, silica and anorganic polymer.
 7. A chromatographic apparatus comprising a columncontaining a substrate having adsorbent particles bonded thereto througha medium comprising a siloxane polymer, said particles comprising anucleophilic composition and have an average particle size of betweenabout 0.1 and about 10μ.